[kubeadm] use v1beta3 configuration version

* extra admission controls now don't have a version in their file names
  eventratelimit.v1beta2.yaml.j2 -> eventratelimit.yaml.j2
* cri_socket variable includes the unix:// prefix to be conformat with
  upstream

roles/kubernetes/control-plane/templates/eventratelimit.yaml.j2

@@ -0,0 +1,11 @@
+apiVersion: eventratelimit.admission.k8s.io/v1alpha1
+kind: Configuration
+limits:
+{% for limit in kube_apiserver_admission_event_rate_limits.values() %}
+- type: {{ limit.type }}
+  qps: {{ limit.qps }}
+  burst: {{ limit.burst }}
+{% if limit.cache_size is defined %}
+  cacheSize: {{ limit.cache_size }}
+{% endif %}
+{% endfor %}